Sailing craft

ABSTRACT

A sailing craft including a hull assembly ( 1,2 ), keel ( 3 ) and turret assembly ( 5 ) connected to the hull assembly ( 1, 2 ), for rotation about an axis. Turret assembly ( 5 ) is adapted to carry the craft&#39;s crew. The craft further includes mast ( 7 ) connected to and projecting from turret assembly ( 5 ) and sail assembly ( 8, 9, 10 ) connected to mast ( 7 ) in spaced relation to turret assembly ( 5 ). Sail assembly ( 8, 9, 10 ) includes sail member ( 8 ) which is movable relative to mast ( 7 ) for propelling the craft. Sail assembly ( 8, 9, 10 ) further includes wind vane ( 10 ) operable to position sail member ( 8 ) with respect to the wind direction. Sail member ( 8 ) may comprise an aerofoil shaped body. The combined center of mass of turret assembly ( 5 ), sail assembly ( 8, 9, 10 ) and the crew is designed to lie close to the rotational axis of turret bearing ( 6 ) while sailing.

The present invention relates generally to sailing craft.

Conventional sailing boats use movable mass or buoyancy to balance thecapsizing moment caused by the sail force. This mass may be part of thekeel, the actual crew on the windward side of the boat, water pumpedbetween tanks, or many other methods which move the centre of mass tothe windward side of the boat. Buoyancy moves as the craft tilts andmore water is displaced on the leeward side of the hull, or the leewardhull in the case of a multi-hulled craft. Under steady state conditionsthe three moments must be balanced.

Absolute stability may only be achieved by positioning the sailing craftcentre of mass below its centre of buoyancy. This carries a huge weightand wetted area penalty, which makes such craft slow. High speed sailingcraft must rely on wide or multi-hull designs and/or movable ballast,usually crew, to achieve stability.

Hydrofoil craft use underwater foils to balance the capsizing momentwithout moving masses but they do produce the same moment, puttingsimilar stresses on the structure. The total foil force must always begreater than the total craft weight, inducing more parasitic drag in thefoils than if the foils were supporting the craft weight alone.

Sailing craft are known which have tilted sail-sails, with the intentionof reducing water drag by supporting at least part of the craft on air.The main problem encountered by the most successful of such craft hasbeen instability due to rapid changes in the moments at play. This isalso a significant problem with most conventional high speed sailingcraft.

All prior art sailing craft achieve equilibrium by balancing large andoften rapidly changing moments. High speed sailing craft, as discussedabove, cannot be inherently stable and so must sail at the limit oftheir ability to balance these moments. The fastest boat in a race istherefore usually the one closest to capsizing.

It is an object of the present invention to provide an improved sailingcraft which alleviates one or more of the aforementioned problems.

According to the present invention there is provided a sailing craftincluding a hull assembly, a keel operatively connected to said hullassembly, a turret assembly operatively connected to said hull assemblyfor at least partial rotation relative thereto about a rotation axis,the turret assembly when in use being adapted to carry the craft's crew,a mast operatively connected to and projecting from the turret assembly,a sail assembly operatively connected to the mast in spaced relationfrom the turret assembly, said sail assembly including a sail memberwhich is movable relative to the mast and which is adapted to catch thewind so as to provide a force for propelling the craft, the sailassembly further including wind responsive means such as for example avane operable to position the sail member with respect to the winddirection.

Preferably, the arrangement is such that when the craft is in a normalsailing mode the major forces acting on the craft are substantiallydirected through the region of a single point. Preferably, the sailassembly, mast, turret and crew have a centre of mass which is at or inthe vicinity of that region of the single point. The position of thecrew on the turret assembly can be changed so that the position of thecentre of mass can be changed.

In one preferred embodiment, the hull assembly has a horizontal planewhich is generally parallel to the water upon which it floats when inthe normal sailing mode, the rotation axis of the turret assembly beinggenerally vertical to the horizontal plane. Preferably, the centre ofmass is in the region of the rotation axis of the turret assembly.Preferably, the hull assembly has a centre of buoyancy and the keel isoperatively connected to the hull assembly in the region of the centreof buoyancy.

Preferably, the mast has a longitudinal axis which is from 15° to 75°from the horizontal plane of the hull assembly. Preferably, when in thenormal sailing mode the longitudinal axis of the mast passes through theregion of the centre of mass.

Preferably, the sail member is operatively connected to the mast formovement relative thereto about 3 axes rotation. Preferably, the sailmember is adapted to pitch, roll and yaw with respect to the mast. Thesailing craft may further include a rudder for steering the craft.

Preferably, the sail member includes a generally aerofoil shaped body.In one preferred form, the sail includes a frame member with theaerofoil shaped body attached thereto and the wind responsive meansbeing operatively connected thereto. Preferably, the sail includesregulating means such as an elevator which is adapted to change theangle of attack of the aerofoil shaped body.

In one preferred embodiment, the turret assembly includes a main bodyhaving opposed end portions, the axis of rotation being disposed betweenthe end portions, the mast being operatively connected at one endportion and the crew support section being disposed towards the otherend portion with the axis of rotation being between the mast and thecrew support section. The turret assembly may be temporarily preventedfrom rotation if desired so that the craft is substantially steered bythe wind.

According to a preferred form the sailing craft alleviates high speedcontrol problems by directing substantially all major forces acting onthe craft through one point or region when in the normal sailing mode.This effectively eliminates the moments which change too rapidly for thehelmsman to control when the wind shifts in speed and direction. Windspeed changes on the sailing craft produce only acceleration ordeceleration in the intended direction of travel, with no significanttendency to capsize, change course or pitch forward.

A primary benefit of the sailing craft of the invention in its preferredform is that water drag may be reduced by supporting some of the craftweight in a controllable way. The propulsive force available is limitedonly by sail force and the mass of the boat. At that limit the craft iscompletely or substantially clear of the water except for the keel and,optionally, the rudder. The resultant low drag allows very high speed.

The fastest way of sailing the sailing craft is to have only its keel inthe water. Excessive sail member force will not tend to capsize thecraft, but will lift it until the wetted keel area is insufficient togenerate enough lift to balance the sail member force. If this happensgradually, the keel efficiency will drop, the boat will lose speed,possibly slip sideways in the downwind direction, and drop lower in thewater due to lower apparent wind speed and a consequent reduction of thesail force; that is, it recovers from crew error without a significantpenalty like a capsize. If the sail member force rises rapidly the craftbecomes completely airborne, it will accelerate sideways (downwind)without the side force of the keel to balance the sail member force sidecomponent, lose airspeed as it gets carried with the wind, the severityof the landing depends on the height of the jump, but the skill of thecrew, and the design of the craft would make such a manoeuvre possiblewithout damage.

Two automatic operation modes are possible—steering or sail setting.Firstly, with a conventional rudder turning the hull assembly to thedesired course and allowing the sail member to automatically drive theturret assembly to the optimum angle. Secondly, as the turret assemblymaintains an almost constant angle to the wind when the sail member isloaded, and resists rotation from its optimum position, the hullassembly may be turned with respect to the turret assembly without usinga rudder. The turret assembly pivot may also be temporarily locked tomake the craft automatically keep a substantially constant bearing withrespect to the apparent wind direction. As the craft changes speedhowever, it will change bearing with respect to the true wind direction.

The mast of a conventional craft is subject to high and variable loads.The mast and associated structure of the proposed craft is subject to abending moment due to the weight of the sail member at rest, but thismoment remains substantially constant under all sailing conditionsprovided the mast is substantially in line with the sail member force.The sail member force imposes only a relatively small and substantiallytensile stress to the mast. The structure may therefore be made lighterand more flexible than in prior art craft.

Preferred embodiments of the invention will be hereinbefore describedwith reference to the accompanying drawings, and in those drawings:

FIG. 1 is a schematic view of a sailing craft according to the presentinvention;

FIG. 2 is a plan view of the craft shown in FIG. 1;

FIG. 3 is a side elevation of the craft shown in FIGS. 1 and 2;

FIG. 4 a schematic illustration of the turret for a range of port tacks;

FIG. 5 is a schematic illustration of one form of a sail force controlmechanism;

FIG. 6 is a schematic illustration of another form of a sail forcecontrol mechanism;

FIGS. 7 to 9 illustrate a form of roll mechanism;

FIGS. 10 and 11 illustrate a form of anticapsizing mechanism.

Referring in particular to FIGS. 1 to 3 there is shown a sailing craftwhich includes a hull assembly comprising one or more hulls 1 connectedrigidly or flexibly to each other by a frame 2, a keel or centreboard 3is attached to the hull assembly near the centre of buoyancy of the hullassembly. A rudder 4 may be attached aft of the keel but is notnecessary. The craft further includes a turret assembly 5 is attached tothe hull assembly by a bearing 6 with a vertical axis which passes closeto the centre of lift of the keel. A mast 7 is operatively connected tothe turret assembly and is attached at an angle of 45°±30° from thehorizontal when sailing. The mast angle may be fixed or variable toassist in rigging and allowing the sail member to be raised forincreased clearance from the water in choppy conditions. The craftfurther includes a sailing member 8 or sail assembly 8, 9, 10, pivotallyattached near its centre of lift to the free end of the mast by controljoint 11. The sail assembly may have a tailplane comprising an elevator9 and a fin 10.

The hull assembly 1-4 provides, as with any conventional sailing craft:buoyancy to support the weight of the craft, and a keel forceperpendicular to the direction of travel as a reaction to that componentof the sail force. It may also provide stability against pitch or roll.

The turret assembly 5-7 provides accommodation for the crew andtransmits the sail member force, through the mast 7, to the centre ofthe craft. It is able to slew, like the turret on a military tank, aboutthe vertical axis with respect to the hull assembly, to allow travelthrough the water in any direction normally possible in a conventionalsailing craft. FIG. 4 illustrates that for all points of sailing, thesail is forward of the turret bearing axis so that the turret needs onlyto travel through an angle of approximately 180°, unless the craft needsto be sailed backwards.

The turret assembly may be linked to the keel such that its onlyrotational degree of freedom is about its vertical axis. Howeverflexibility about horizontal axes may be used to allow the turretassembly to remain steady while the hull assembly tilts in response towaves. In this case, if the turret assembly tilts about any horizontalaxis, the keel tilts with it by the same angle. This is particularlyimportant regarding tilt about the transverse axis (horizontal andnormal to the direction of travel). Referring to FIG. 3: this means thatif the turret assembly 5 with all attachments including the mast 7 andsail 8, rotates clockwise in the plane of the page, the keel 3 willrotate by substantially the same angle in the same direction. For smallangles, this minimises changes in the vertical force component 33 as thecraft rolls in a swell, thereby reducing any tendency for the craft torise and fall under such conditions. For example, a 10° clockwise rollangle will increase the vertical lift component 33 by less than 2% forconstant sail force 31 with the described mechanism; whereas with afixed vertical keel 3 under the same conditions, the rise in sail forcevertical component 33 would be almost 18%. If the craft is sailing nearthe point of becoming airborne, such a feature is important forstability.

The sail assembly 8-10 is operatively connected to the end of the mast 7and has three axes of rotation allowed by the control joint 11 describedhere in conventional aircraft nomenclature: Pitch 12, or angle ofattack, is controlled by the crew and determines the force generated bythe sail member in response to the air velocity incident on it. In theembodiment shown in FIGS. 1, 2 and 3 this is done indirectly by changingthe angle of attack of the elevator 9 or directly by pulling the controlline 13. The pitch is increased to produce a higher sail member forceand drive the craft faster. Roll 14 is controlled by the crew, anddetermines the capsizing moment generated by the sail member. In theembodiment shown in FIGS. 1, 2 and 3 this is done by bridle lines 15attached to the or the sail member. The same effect may be achieved bywarping the tips through a lever system within the skin of the sailmember (not shown), or through the use of ailerons (not shown). Roll iscontrolled to keep the craft from capsizing: rolling the sail member inthe direction of the arrow 14 tends to capsize the boat downwind;rolling in the opposite direction has the opposite effect. It ispossible to capsize the craft upwind as well as in the conventionaldownwind direction, but the roll is generally used to keep the craft aslevel as possible without needing to use conventional weight shift.Unlike a conventional craft, if the sail member roll is trimmedcorrectly there is no capsizing moment.

Yaw 16 is controlled by the wind, as with a weather vane, and allows thesail assembly 8-10 to pivot freely about the axis perpendicular to itsmain lifting surface so that it always faces into the wind. In theembodiment shown in FIG. 1 this is done by the fin 10, but may beachieved by using a swept sail member and/or fins.

The sail assembly behaves much like a kite on a string, adjustingautomatically to wind direction and always directing its force away fromthe centre of the craft. During wind direction shifts the force willmove away from this position, causing the turret to swing until itregains equilibrium, much as a kite does.

As discussed the craft exhibits zero moment due to centre of massposition. The combined centre of mass of the turret assembly, sailassembly and crew is designed to lie close to the rotational axis ofturret bearing 6 while sailing. During assembly the mast may be loweredto facilitate said assembly attachment: this may move the centre of masstemporarily. The result is that no substantial moment about therotational axis of the turret bearing is produced by the action ofacceleration in any direction. For example, sudden deceleration causedby hitting a wave will not cause the turret to swing significantly awayfrom its existing angle. Moments about the horizontal axes are alsosubstantially immune to vertical accelerations, including gravity.Moments about the horizontal axes are not balanced under the action ofhorizontal accelerations, however. The vertical position of the centreof mass is almost inevitably above the waterline, but well below thesail member. As the largest horizontal accelerations are produced byforces originating from the sail member or components in the water,there will be unbalanced pitching and rolling moments produced byforward and sideways accelerations respectively. Hitting a wave, forexample, will produce a pitching, bow down, moment. However, the momentof inertia of the turret and sail assembly will help resist pitching.Also, the forward swing of the sail member will move its line of actionin front of the combined centre of mass of the turret and sailassemblies, generating a restoring moment to pitch the bow up again.This is because the sail force direction is substantially constant withrespect to the apparent wind direction. In other words, the sail memberbehaves like a vertical force lifting and object on a string: the objectnaturally tends towards a position directly under the force, even if itstarts to one side.

Because of the arrangement of the various components of the craft itexhibits zero moment due to wind force. Insofar as horizontal forcecomponents are concerned and referring to the plan force diagram in FIG.2 in which the apparent wind direction is indicated by arrow 20. Whensailing under steady state conditions, the line of action of the sailmember force 21 passes through the keel substantially at itshydrodynamic centre of force, the sail force side component 22 issubstantially balanced by the keel horizontal force (not shown), and thethrust component of the sail force 23 is available to overcome drag fromthe keel, rudder and hulls. As there is no significant capsizing momentas shown above, and the centre of mass of the craft is on the fore-aftcentreline of the keel as shown above, the centre of drag of all thewetted parts will be effectively on the line of the thrust component 23.The result is that changes in sail force have no significant tendency toturn the craft.

Insofar as vertical force components are concerned and referring to themast elevation plane force diagram in FIG. 3 in which the apparent winddirection is out of the page towards the reader, when sailing understeady state conditions, the line of action of the sail force 31 passessubstantially through the keel at its centre of force, the wind forceside component 32 is substantially balanced by the keel horizontal forceand overall drag force explained above. The sail force verticalcomponent 33 acts effectively through the centre of mass of the entirecraft, including crew, tending to lift it evenly out of the water.

FIG. 4 shows turret positions for a range of port tacks. The winddirection 20 applies to all directions shown:

Direction 40 is a close reach.

Direction 41 is a beam reach.

Direction 42 is a broad reach. As with conventional high speed sailingcraft, sailing directly downwind will usually be slower between marksthan taking course 42 and jibing to the opposite course.

Starboard tacks are identical to FIG. 4 but mirrored about axis 43 sothat the sail is over the port side of the craft.

Note that the sail angle of attack is similar to that of a conventionalsailing craft, being close to parallel to the direction of travel in theclose reach, and progressively further away from parallel as the courseswing to broad reach.

The craft must operate most of the time with at least some of the keelin contact with the water, as the keel force prevents the craft sideslipping with the wind. The highest efficiency is achieved with all butthe keel out of the water, so it is important to control the height oflift accurately. This can be done by controlling the sail force or thekeel force direction either manually or automatically. The sail force isthe obvious first choice as it must be controllable to prevent damage inhigh winds. Sail force may be controlled by allowing the joint 11 inFIG. 1 to be extendible and spring loaded against the sail force.

A preferred embodiment of the sail force control mechanism is showndiagrammatically in FIG. 5, in which the air flow direction is shown bythe arrow 2. The mechanism comprises a sail keel tube 17 on which thesail 8 is substantially rigidly mounted, and the elevator lever 49 isattached at the pivot 50. The elevator 9 is rigidly attached to theelevator lever and driven by it.

The sail keel tube 17 is attached to the sail slide 51 at pivot 52 whichallows the sail to change angle of attack and therefore its lift force,under the action of the elevator 9 down force 53. The sail slide 51 isfree to slide over a limited stroke in the fork 54 which is connectedvia the remainder of the sail control joint 11 shown in FIG. 1 to thetop end of the mast 7 also shown in FIG. 1. The slide may be supportedby rollers 55 or other friction-reducing means. The slide 51 is pulleddown by the sail load tension spring 56. The spring may be aconventional spring or a long length of rope or cable of knownelasticity. The elevator control cable 59 is attached to the elevatorlever 49 at the pivot 60, then runs around the pulley 61 attached to thesail keel tube 17, then around the pulleys 62 and 63 which are attachedto the fork 54, then to the sail slide 51 at attachment point 64. Thecable tension is opposed by the elevator return spring 65 which ispivotally mounted between the elevator lever 49 at 66 and the sail keeltube 17 at 67.

The helmsman is able to select any desired sail load which will remainsubstantially constant, independent of wind or boat speed. The sailforce control mechanism functions as follows:

If FIG. 5 shows the mechanism at equilibrium, then an increase in sailforce 21 due to a wind gust will extend the sail load spring 56,;raising the sail slide 51. Cable 59 is consequently slackened, allowingthe elevator 9 to be pulled down by the elevator return spring 65,reducing the elevator force 53 due to the lower angle of attack. Thereduced elevator down force allows the tail to rise, reducing the sailangle of attack and therefore the sail force 21.

Depending on damping, the mechanism may oscillate slightly beforesettling to a sail force slightly higher than the original set point.

The basic sail control mechanism is shown diagrammatically in FIG. 5 issensitive to changes in angle of attack such that as the sail rotatesclockwise, the cable length shortens between pulleys 61 and 62. Thiswill cause the elevator position to change independently of movement ofthe sail slide 51 with respect to the fork 54. Depending on the actualdimensions of the mechanism, this could cause undesirable effects.

A further preferred embodiment of the sail force control mechanism isshown diagrammatically in FIG. 6, in which the air flow direction isshown by the arrow 20, operates independently of the sail angle ofattack. The mechanism comprises a sail keel. tube 17 on which the sail 8is substantially rigidly mounted, and the elevator lever 49 is attachedat the pivot 50. The elevator 9 is rigidly attached to the elevatorlever and driven by it. The sail keel tube 17 is attached to the sailslide 51 at pivot 52 which allows the sail to change angle of attack andtherefore its lift force, under the action of the elevator 9 down force53. The sail slide 51 is free to slide over a limited stroke in the fork54 which is connected via the remainder of the sail control joint 11shown in this FIG. 1 to the top end of the mast 7 shown in this FIG. 1.The slide may be supported by rollers 55 or other friction reducingmeans. The slide 51 is pulled down by the sail load spring 56 force 57.The elevator control cable 59 is attached to the elevator lever 49 atthe pivot 60 at one end, and the housing of a free pulley 67 at theother. A second cable 68 is attached to the sail slide 51 at 64, thenwraps around the pulleys 69, 70, 67, 71, 72 and 73, then back to thesail slide 51 at attachment point 64. Pulley 67 is constrained only bythe cables 59 and 68 attached to it. Pulleys 70 and 72 are substantiallythe same diameter, although shown different diameters for clarity, andhave their pivots substantially coincident with the sail slide pivot 52.Pulley 71 has its pivot on the sail keel 17 or any part mountedsubstantially rigidly to it. Pulleys 69 and 73 have their pivots on thefork 54. The cable tension is opposed by the elevator return spring 65which is pivotally mounted between the elevator lever 49 at 66 and thesail keel tube 17 at 67.

Operation is substantially the same as for the basic power controlmechanism in that movement of the sail slide 51 down into the fork 54pays out cable 68 causing pulley 67 to move to the right, reducing theelevator angle. The improvement lies. in the fact that as the angle ofattack changes, pulleys 70 and 72 respectively unroll and roll upsubstantially the same length of cable. The pulley 67 therefore rotatesas the angle of attack changes, but its centre does not move, so thatthe elevator angle does not change. This allows the sail to keep asubstantially constant force while the mast swings with respect to it,reducing instability of the control system due to inputs from unwantedsources.

The craft has no inherent stability against capsizing once its hullshave lifted from the water. A preferred configuration is a trimaran withsmall outriggers which remain in contact with the water after the mainhull is airborne to give some capsize stability with minimum drag.During high speed runs, the crew could raise the outriggers from thewater and control the sail roll manually. During long runs theoutriggers provide a direct anti-capsize moment through buoyancy orplaning, or pivot upwards to drive an automatic mechanism on the sail.For example, ropes joining each outrigger to each side of the sail insuch a way that a capsizing tilt would make the sail more horizontalwould prevent capsize if the sail roll produced was significantlygreater than the capsizing angle, relative to the boat.

A preferred embodiment of the sail roll mechanism, which is part of thesail control joint 11, is shown in FIG. 7 in the normal runningposition, and in FIGS. 8 and 9 in die sail horizontal position. Themechanism comprises the following major assemblies. Firstly the maincradle assembly 80, shown crosshatched in FIGS. 7 and 8, which issubstantially rigidly attached to the top end of the mast 7 shown inFIGS. 1, 2 and 3. Secondly the pulley segments 81 and 82 which aresubstantially rigidly attached to the sail yaw journal 83. The latterforms the inner part of the sail yaw bearing which also forms part ofthe sail control joint 11 and allows the sail to yaw so that it alwaysfaces the apparent wind like a weather vane. The control cable 84 hasits end fixed to the pulley segment 81 at 85, it wraps around the pulleysegment 81, before passing over pulley 86, then down the mast (notshown). The control cable 87 has its end fixed to the pulley segment 89at 88, and wraps around the pulley segment 82, before passing overpulley 89, then down the mast (not shown).

The purpose of the mechanism is to remotely roll the sail clockwise oranti-clockwise by pulling the two cables 84 and 87 respectively. Thismay be done by driving the sail structure directly, functionallyidentical to cables 15 in FIG. 1, or by driving ailerons or someequivalent prior art aeronautical device which uses air flow to causethe sail to roll. The mechanism is shown in FIG. 7 in the normal runningposition as in FIGS. 1 to 4, and in FIGS. 8 and 9 in a position whichwould make the sail substantially horizontal.

A preferred embodiment of the automatic anti-capsizing mechanism isshown in schematic diagrams in FIGS. 10 and 11. The mechanism comprisesthe following major parts and assemblies. The outrigger assembly 100,comprising floats 101 cross beam 102 and control lever 103. The mainhull and mast assembly 104 which behaves as a substantially rigid bodyand comprises a main hull 105, mast 7, control housing 106, and the sailcontrol joint 11 represented as a simple pivot for the sake of clarity;details are shown in FIGS. 7, 8 and 9; the sail 8 which may becontrolled directly or as described above; the roll control slide 107shown supported by four wheels 108, slidably mounted within the guidesof the control housing 106, and driven by pin 109 attached to controllever 103; The rollset-point lever 110, which is pivoted on the mainhull and mast assembly 104, at 123; pulleys 111, 112, 113 and 114 eachwith pivots attached to the main hull assembly 104; pulleys 115 and 116both with pivots attached to the roll control slide 108; the controlcable 117 is attached to the sail 8 at 118, passes around pulleys 111,114, and 116 then attaches to the roll set-point lever 110 at 119; thecontrol cable 120 is attached to the sail 8 at 121, passes aroundpulleys 112, 115 and 113 then attaches to the roll set-point lever 110at 122.

Operation of the automatic anti-capsizing mechanism, with the winddirection being substantially perpendicular to the page, is as followsunder steady state conditions as shown in FIG. 10, the sail force passesthrough the centre of lift of the keel, producing no capsizing moment.The roll set-point lever 110 is locked in the position set by the crew.When a disturbance starts to capsize the craft as shown in FIG. 11, theoutrigger assembly 100 stays substantially horizontal so that theattached lever 103 pushes the roll control slide 107 to the right, whichslackens cable 120 and tightens cable 117. The sail assembly 8 istherefore driven clockwise, rotating the line of action of its liftforce to the left of the keel. This produces a clockwise moment whichtends to bring the craft back to the horizontal. If, for any reason thecraft tends to list under steady-state conditions, the roll set-pointlever 110 may be adjusted by the crew until the craft is horizontal orat another desired angle: the mechanism then works to maintain the newset point. Note that as with all such proportional controls (where therestoring action is proportional to the deviation from the set point),the control will not restore the craft exactly to the set position, butwill behave much as a conventional ballasted keel sailing boat and heal,but not capsize.

Finally, it is to be understood that the inventive concept in any of itsaspects can be incorporated in many different constructions so that thegenerality of the preceding description is not to be superseded by theparticularity of the attached drawings. Various alterations,modifications and/or additions may be incorporated into the variousconstructions and arrangements of parts without departing from thespirit or ambit of the invention.

The claims defining the invention are as follows:
 1. A sailing craft including a hull assembly, a keel operatively connected to said hull assembly, the hull member having a generally horizontal plane which is generally parallel to the water upon which it floats when in a normal sailing mode, a turret assembly operatively connected to said hull assembly for at least partial rotation relative thereto about a rotation axis, the turret assembly when in use being adapted to carry the craft's crew, a mast operatively connected to and projecting from the turret assembly, said mast having a longitudinal axis which is inclined to the horizontal plane of the hull assembly when in the normal sailing mode, a sail assembly operatively connected to the mast in spaced relation from the turret assembly, said sail assembly including a sail member which includes a generally aerofoil shaped body which is pivotally movable relative to the mast and which is adapted to catch the wind so as to provide a force for propelling the craft, the sail assembly further including wind responsive means which is operable to position the sail member with respect to the wind direction.
 2. A sailing craft according to claim 1 wherein when the sailing craft is in its normal sailing mode the major forces acting on the craft when it is being sailed are substantially directed through a region of a single point.
 3. A sailing craft according to claim 1 wherein the sail assembly, mast, turret and crew have a centre of mass which is at or in the vicinity of said region of the single point.
 4. A sailing craft according to claim 1 wherein the rotation axis of the turret assembly is generally vertical to the horizontal plane.
 5. A sailing craft according to claim 1 wherein the centre of mass is in the region the rotation axis of the turret assembly.
 6. A sailing craft according to claim 1 wherein the hull assembly has a centre of buoyancy and the keel is operatively connected to the hull assembly in the region of the centre of buoyancy.
 7. A sailing craft according to claim 1 wherein the longitudinal axis of the mast is inclined from 15° to 75° from the horizontal plane of the hull assembly and when in the normal sailing mode passes through the region of the centre of mass.
 8. A sailing craft according to claim 1 wherein the sail member is operatively connected to the mast for movement relative thereto about 3 axes of rotation.
 9. A sailing craft according to claim 1 further including a rudder for steering the craft.
 10. A sailing craft according to claim 1 wherein the sail member includes a frame member with the aerofoil shaped body attached thereto and the wind responsive means being operatively connected thereto.
 11. A sailing craft according to claim 1 wherein the sail member includes regulating means controlled by the crew, which is adapted to change the angle of attack of the aerofoil shaped body.
 12. A sailing craft according to claim 1 wherein the turret assembly includes a main body having opposed end portions, the axis of rotation being disposed between the end portions, the mast being operatively connected at one end portion and the crew support section being disposed towards the other end portion with the axis of rotation being between the mast and the crew support section.
 13. A sailing craft according to claim 1 further including means for controlling movement of the sail member at the turret assembly.
 14. A sailing craft according to claim 1 wherein the turret assembly is temporarily prevented from rotation so that the craft is substantially steered by the wind.
 15. A sailing craft according to claim 1 wherein said wind responsive means is a vane.
 16. A sailing craft according to claim 11 wherein said regulating means is an elevator. 